Jet engine simulator for flight training equipment



1961 J. F. GUlLL OUD 3, 68

JET ENGINE SIMULATOR FOR FLIGHT TRAINING EQUIPMENT Filed June 27, 1958 3 Sheets-Sheet 1 8 R g, k stave 5c FUEL CONSUM- STOP ---E-- I! -lsM2]- sp rum/s7 CD t E R -t'll--' CV snmr ll: g R T cv ,1 R SERVO 1 m5: n01: ..E- 5 1 i CP C! Q 41 Q R 50 ruuonzrn szow I J'Pfl'lOF-ROZ' F s11 cm 1 com. 1X ans HEIGHT H SPEED INVENTOR.

JEAN FERNAND GU/LLOUD Dec. 5, 1961 3,011,268

JET ENGINE SIMULATOR FOR FLIGHT TRAINING EQUIPMENT J. F. GUlLLOUD 5 Sheets-Sheet 2 Filed June 27, 1958 M MW I MT M6 al O WU A N 7 .0 5 MWA R. K mg n m r N 1 v. m mw w a C v W E 3 2 A m M WW4? B W m w Ow ll 5m W Wm m R p c M w m a I m 5 D 3.. m eM l "o a m m 3 as I. S M 6 T d m id I N Mi I F T. I I 2 0 w I} N o I M m a L W u- P H W? 7 M 9w!- .m I 2 D i flll'. A r P C i J a I I Iv M Dec. 5, 1961 J. F. GUILLOUD 3,011,268

JET ENGINE SIMULATQR FOR FLIGHT TRAINING EQUIPMENT Filed June 27, 1958 3 Sheets-Sheet 3 M N}?! M- e-MMH A AMP/. NR2 H H ALT. (A/A) 1 (M?) SPEA'I FIG. 4A FIG. 48

PILOT Ali AMPL. M07 P07 V- A a: F

AMPLMOII Inc/1. par r/mu'ir Fan con/30M IN VEN TOR. FIG 6 JEAN FERN/IND GU/LLOUD condition during flight.

United States Patent The present invention relates to an improved device for simulating the operating and utilization conditions of a jet engine on board an airplane, as used in flight training equipments having the same control and monitoring apparatus as an actual plane and controlling analog devices of the automatic computer type to simulate responses of actual airplane equipments.

The invention more particularly relates to the simula-- tion of jet engines which, in their actual operation, are provided with automatic regulating means for controlling the speed of rotation of the turbines and the temperature of the gas entering these turbines. at optimum admissible values for any condition chosen. These conditions are set by the user through the power control means of the jet engines in the simulator equipment. Such regulation is usually provided, in actual practice, by a tachometer regulator mounted on the shaft of the engine concerned. The gas temperature is regulated by varying the cross section of the ejection blast pipe of the burned gases.

In actual practice further, this regulator ensures an automatic. start, the successive phases of which are controlled through a clock mechanism acting to operate the different equipments and corresponding circuits of the airplane. Once the start is made, this clock mechanism breaks thecircuit of the starting fuel, which is separate from the fuel supply, circuit for normal flight; it also.

cuts off the ignition circuit. From this point on, the condition of operation of the engine only depends upon the power control actuated by'the pilot of-the plane, which acts upon the regulator control lever. The starting operation is of course initiated by the pilot; however, he can make'it effective only after satisfying a certain number of regulation actions, viz, connection to a park supply, actuation of a switch controlling the fire valves, actuation of another switch starting the fuel pump and lastly, actuation of a further switch to protect the engine which puts the clock mechanism in operative condition.

As flight defaults may occur which are to be simulated the pilot must be able to control re-ignition during the flight; this is actuated by a two-position switch which in its normal position places the equipments and circuits in the ground condition, and which in its re-ignition position places equipments and circuits in re-ignition normal, the equipments and circuits are such that they permit the normal development of the automatic cycle of phases in starting operation. When this switch is brought to re-ignition, equipments and circuits are so varied that the circuit for the starting fuel and the electric ignition circuit are brought into operative condition simultaneously.

In the flight simulator further, the pilot can actuate an inverter switch for i nition and ventilation, res ec-,

tively. He may thus elect to ensure on ground the ventilation of an engine and check the good operating condition of the starting clock mechanism. When he places When this switch is placed onv this switch on ventilation, a program is automatically switch on ignition, the Starting operations take place 3,011,268 Patented Dec. 5, 1961 "ice this position is passed (during the starting period), the speed of rotation of the turbine is made a function of the position of the power control proper.

Since the automatic regulator, during the slowed condition thereof, causes the speed of rotation to be limited to a minimum value compatible with'the activation of the combustion chamber, it should be noted that there exists a dead span on the gas control handle (following its slow" position) which is a function of thealti- 'tude of the plane.

Stopping an engine on the ground is caused by the pilot bringing the control handle to its stop position. The engine will of course continue.

On the other hand, re-ignition during flight can only be feasible when certain conditions are met, and these conditions depend on altitude and speed of the plane and on the speed of rotation of the engine concerned at the time of re-ignition following the incident which makes such re-ignition necessary. Thus, regulation is controlled by the action of the automatic regulator after the pilot has complied with the operations permitting the initiation of such a re-ignition during flight.

In a flight simulator equipment, the monitor must possess means for simulating such a breakdown of an engine-so that he may check the reactions of the pilot under training. The monitor must also have means to' v A simulator device for' a flight simulator equipment or plant relating to the simulation of a jet-engine must sup-" ply the pilot with an uninterrupted indication or display of the speed of rotation of the engine and preferably also an uninterrupted indication or display of the temperature of the blast pipe for the burned gases. These indications and other data available in such a plant, such as relating to thrust and fuel consumption, may control analog computers for displaying to the pilot the values of such flight parameter data.

One of the objects of the invention is to provide a simulator for jet-engine operation and actuation satisfy ing all the aforementioned conditions. I

Another object of the invention is to simulate jetengine operation and actuation by deriving a turbine speed from an analog computer wherein at least one shaft is driven in linear relation with the computed speed through a servo-mechanism receiving the output signal of a summing amplifier having inputs which receive analog voltages, each representative of a definite speed corresponding to a distinct condition of control of the turbojet engine and to a control of the engine under this condition, these analog voltages being routed to the inputs of the summing amplifier through a selector switch operated by the engine control sets of both pilot and monitor and also under the control of data generated by, the servomechanism itself.

A further object of the invention provides certain additional arrangements to enhance its efiiciency, such as certain program circuits for some of these analog voltages, which are mainly derived from potentiometers determining the laws of relative change as a function of flight parameters and manual and/or automatic controls in the flight simulator equipment.

These and other objects of the invention will be more fully understood from the accompanying drawings, wherein:

FIG. 1 shows in block diagram a device according to the invention.

FIGS. 2 and 3 if placed side by side, FIG. 2 on the left and FIG. 3 on the right, and connected through terminals I to- XI, show in detail a speed computer such as shown in FIG. 1 for simulating the rotation of a jet-engine turbine.

FIGS. 4A and B exemplify function transducers such as shown as blocks in FIG. 2; and represents slow and free engine rotations, respectively.

.FIG. 5 shows a circuit simulating blast pipe temperature to be connected through shaft N1 to the device shown in FIGS. 2 and 3, in accordance with the overall scheme of FIG. 1 and,

FIG. 6 exemplifies a servo-mechanism to be connected through terminal X to the device of FIGS. 1 and 2 also in accordance with the block diagram of FIG. 1 for driving further simulator arrangements relating to the thrust and fuel consumption of the plane.

Referring to FIG. 1, A represents a summing amplifier provided as usual with a number of input resistors and one feedback resistor, all adjustable and being referred to as R. The amplifier proper is of high gain as conventional in such summing amplifiers.

The output of A is fed to a servo-mechanism 8M driving a shaft N which mainly controls a tachometer indicator T and which will also control, when required, a computer S0 for the simulation of the blast pipe temperature of the engine concerned. Computer 50 is further controlled from an overall input CV representative of certain flight conditions which will be later defined.

The output of A is also fed to a further servo-mechanism 8M driving a shaft N to drive when required further simulating computers such as SC and SP for the computation of fuel consumption and thrust, respectively, of the engine. These computers are unrelated to the invention and therefore, not described in detail.

Each of the input resistors of summation amplifier A is adapted to receive an analog voltage representing a particular simulation parameter. This will occur any time a corresponding path is established through routing switch CA, the structure and operation of which will be further explained below. It is sufficient to assume that routing switch CA is controlled in the first place by control CD resulting from actions of a pilot and a monitor, and in the second place, by a control or feedback line CR resulting from the conditions of the computed speed of engine rotation derived from servo-mechanism 8M These input analog voltages may be stated as follows:

A voltage issuing from a program device MG related to' the speed of turbine rotation and controlled by the pilot actuating the gas handle at CP.

The voltage of MG, however, is applied to routing switch CA only when contact is in a suitable position; and

In another condition of contact c an analog voltage representing a slow condition and issuing from a device NR-is applied to CA.

The change-over of the contact on c is controlled from a comparator S1 receiving on its inputs the voltages issuing from MG and NR, respectively. The program of NR is determined by the flight conditions, and its corresponding control.

Program device NA produces a voltage .simulating'the free rotation of the engine; NA is controlled by the flight conditions through a corresponding control input CV.

The above two analog voltages may be considered as relating to normal flight; to these voltages there are added unit PV is initiated under control of the pilot and, once activated, simulates the actions of the clock-mechanism for such a ventilation;

An analog voltage issuing from a stopping program unit PA is controlled by the pilot (normal control) as well as by the monitor (simulation of a false starting of the engine) through two control inputs of the type shown in FIG. 1 at CPM.

An analog voltage issuing from re-ignition during flight program unit PRV is controlled by the pilot through input CPA but only is effective when the pilot has conformed to the other actions and when the flight conditions are otherwise satisfactory.

The programs for stopping the engine and re-igniting it during flight are based on experiments. i

The operation of the arrangement of FIG. 1 may be stated as follows:

As long as the simulated flight is not initiated, summing amplifier A will not receive any analog voltage at its in puts and its output will be zero. At the beginning of a simulated flight, the pilot actuates the starting organs for the engine and the automatic starting program is initiated at PD. This operation may occur after an operation of ventilation of the engine has been performed. In this case, program PV has been previously initiated and has automatically proceeded until its end.

The ventilation program analog voltage has beenapplied first to A Now, when during the course of the starting program, the monitor causes the simulation of a false start, the program from PD stops and the pilot is obliged to actuate again the control of initiation and activation of PD. As soon as starting program PD is terminated, the slow speed program is activated; an analog voltage issues from NR and contact 0 is in its lower position (shown in the drawing). Since, the pilot controls the gas admission to the engine upon passing from slow to normal speed, automatically, at minimum normal speed, comparator S1 will operate to bring c to its upper position in which voltage MG will reach the input of amplifier A during the slow rotation period; the monitoring operator may intervene if he desires, thus causing the activated engine to stop. Since the stopping program has interfered in response to the monitors action, as in the present case, during the start period of the simulated flight, it is now up to the pilot to renew his controls for starting the engine again. Once this flight is normally proceeding, the monitor may want to simulate a default and stop the engine. The pilot must then take the necesaltitude and speed, are satisfied. In case, during a simulated flight, the pilot controls the slowing down of the engine, there is, as stated above, a dead span on the pilot controls which permits the comparator SI to detect the passing of the slow speed value reached. by the engine under the control of the pilot to the value of maximum slow speed within the program unit NR. At that in-' stance, contact 0 is returned to its lower position and voltage NR-is applied to A In case the flight is terminated by an action of the monitor, the free-rotation program is activated; such free-rotation program is also activated when a fault of the engine has been simulated by the monitors control during the flight. The latter case lasts until the re-ignition program is initiated. In all these cases, the free-rotation program has participated in the operations in an instant at whichthe pilot acts to correct the default.

Program units and routing circuits, as well as servomechanism 8M driving tachometer T, will be described in detail with reference to FIGS. 2 and 3, and furthermore, with reference to FIG. 4 (block units NRNA of FIG. 2 are specified in FIGS. 4A and B respectively as an example). e

The gas handle in its actual shape and structure, as available to the pilot in the flight simulating equipment, is not shown and merely indicated as an axis MG driven by it. Axis MG carries a control cam CG and a pair of identical potentiometers MG1 and MG2 on each of which is plotted the law of variation of the speed of rotation of the turbine as a function of the position of gas handle MG. When this control cam CG is in position stop, the abutment CG; on the cam CG maintains open an electrical contact CG and a battery voltage +b will act to energize light v (at the monitoring set). In the drawings, all lights are referred to as v, forming part of an obvious display at the monitors-desk of the conditions of the simulation equipment with respect to the pilotsactions. I

Program units NA and NR are shown in FIGS. 4A and B to be under control of two parameters H and V height and speed of the airplane concerned and as computed in the flight mechanics parameter computer of the flight simulator. These parameters may be available for instance an angular positions of shafts driving the movable parts of potentiometers representing experimental laws for deriving the output voltages. These and other potentiometer arrangements, defined further below, are

therefore analog-type function transducers well known per se. As apparent from FIG. 4B, analog voltage NA is the result of summation at A of the two voltages. One voltage is actuated by parameter M and fed by a constant voltage supply. The other voltage issues from a potentiometer actuated by parameter V; and fed by the output voltage of a further potentiometer actuated by parameter H and fed by a constant voltage supply. Similarly, as apparent from FIG. 4A, the two voltages NR and NR made equal, are derived as the result of the summing at A of two voltages issuing from potentiometers actuated -by the parameter V H.. One of .these voltages, V,, receives a constant voltage supply and the other H, the output voltage of a potentiometer actuated by the parameter V and fed from a constant voltage supply. There is no need to define the laws and formulations of such'combinations. The are based on empirical data obtained for each type of airplane.

/Voltages NR and M6 are applied to the inputs of a difierence amplifier S1 which discriminates the sign of the difference and, according to this Sign, controls the positioning of change-over contact c on one or the other of its stationary contacts. These stationary contacts or terminals are connected to the outputs of NR and MG respectively. When the analog voltage NR is higher than MG, the change-over contact is in the position shown; in the opposite case, it is in the reverse position. The switching, obviously, of the analog voltages to slow and pilot controlled speeds is provided automatically in another part of the equipment which-is not related to the conditions of the routing circuits leading to amplifier A The pilot control board is shown as CP in FIG. 3 and includes a push-button D for the control of the starting of the engine, a change-over switch ventilation-ignition and, a change-over switch normal-reignition during flight. Panel CP has also manually actuated interrupting switches: F for the anti-fire valve, P for the fuel pump, and S for the safety of the engine. The ventilation and starting operations can only be effective after the pilot has connected the electrical supply to the park plug PP.

fault occurring during the flight and stopping the engine. The monitors desk is also provided with a manually adjustable potentiomete PR, feeding an additional in put of the summing amplifier A to simulate a default of operation of the regulator of the engine (FIG. 2).

It must be understood that the device shown and described relates to a single engine and must be duplicated for any other engine in the airplane.

The program relating to re-ignition during flight, stopping, ventilation, and starting of the engine, is represented on potentiometers PRVl, FIG. 2, PV, and PD, FIG. 3, respectively. PotentiometerPRVl, and PA is driven by the shaft of motor MR when energized. Cams CR and CR on the shaft of motor MR control by their profiles actuation to-b-reak of contacts introduced in parts of the supply circuitry of relays 29 to 33 included in the program unit. As stated above, the effectiveness of the program when initiated by the pilot depends upon'cer- .tain flight conditions. The occurrence of such conditions is'simulated by means of a pair of work contacts of relay cam CVR- and CHR. These relays are serially connected andeach is controlled from a cam, CVR by Potentiometer PA, FIG. 3, is driven by the'shaft of motor MA; this shaft drives two cams CA and CA controlling contacts which break the supplies of relays 34 to'37 forming part of the unit including PA.

The electrical output X of A in FIG. 2 reaches in FIG. 3 an input of SM the output shaft N of which drives tachometer T. Since the routing circuits are placed under the act-ion of parametric data derived from the output of 5M the structure of 8M will be defined prior to that of these circuits. It comprises as usual an amplifier and a motor driven by this amplifier as shown at B1. The motor shaftdrives a potentiometer P delivering the position control feedback signal as usual. It is further useful to simulate the time constant of the automatic regulator of the engine and consequently a second feedback loop is provided in 5M 'This loop extends from the electrical output terminal of B1 through a summing amplifier AD reversing the polarity of the voltage and through a potentiometer fed by amplifier AD and controlled by the parameter H. Since point XII at the output of AD is separated from the servo-amplifier, it may be used in the routing circuits control to a signdiscriminator S1 this discriminator controls the condition of a change-over contact c in accordance with the direction of variation of the speed of rotation simulated for the engine.

The output shaft of 8M drvies a cam C controlling an electrical contact applying a battery voltage to line I each time the speed of the simulated rotation is lower than a predetermined value, for instance, lower than the value terminating the slow condition in the starting period of the engine.

The routing circuits comprise relays numbered from 1 to 27 and 29 to 30. Some of these relays such as 12 and 56 are shown as single relays while in actual practice relays having more than one pair of armatures may be used. Relay 38 is the relay controlled, through XI, each time conditions of possible re-ignition of the engine during flight are satisfied. -Relay 12 is further activated each time a contact 0 is in the condition shown. This contact is understood as being controlled from the consumption simulating device in its empty condition.

Identification of the relays Relay or relays 1-2 are on each time the speed of rotation of the engine is lower than a predetermined value before reaching the value terminating the slow period of starting of the engine.

Relay 3 is on for each cause of stopping of the engine either:

From lack of fuel, through From the stop position of the gas handle, cam CG applying the battery voltage on IX, relay 14- being on;

From the closed condition of the fire-breaking valve, relay 15 being ofi, change-over F of being on;

From the stopping of the low pressure of the fuel pump, relay 16 being on, change-over P of CP being on; for the reason that in any one of the above cases, relay 12 is on and applies the battery voltage to III. This relay 12 is provided with two separate maintenance circuits: one through the work contact of relay 18 which is on, each time the airplane is at standstill (V;=0) and the speed of rotation of the engine is lower than the above stated value; the other circuit extends through the rest contact of relay 18 when relay 20 is ofi, i.e., when, during a flight, relays 19 and 3-8 are off, relay 17 being obviously off as controlled simultaneously with relay 1-2.

Relay 4 is energized when the engine is on the point of stopping the airplane on the ground; discriminator S1 then controls for displaying a slowing down of the engine, relay 11 is at rest (this relay is only on during a starting period of the engine); relay 10 is on as the airplane is at standstill, and relay 9 is on as controlled by the voltage applied to I simultaneously with relays 1-2 and Relay 6 is on when switch V of CF is placed on ventilation.

Relay 7 is on when change-over R is on reignition during flight, relay 19 being simultaneously controlled with 7.

Relay 8 is brought to work when the fireproof valve is closed or the fuel pump stopped, through corresponding contacts of relays 15 and 16.

Initial conditions Relay 12 is at Work and maintained by the circuit passing through work contact of relay 18 which is at work since Wire I carries the battery voltage, shaft N being at rest.

Relay 1-2 is energized as battery is applied to I.

Relay 3 is energized as relay 12 applies battery to III.

Relay 4 is on through 0 rest contact of 11, Work contact of and work contact of 9.

Relay 5-6 is at rest as ground is applied to wire V through change-over V of CP, in its ignition condition.

Relay 7 is at rest as VII receives the ground potential from change-over R, its condition being normal.

Relay 8 is at work as VIII receives the battery voltage through the rest contact of 15, fire-proof valve F being closed, and through the work contact of relay 16, the low pressure fuel pump being stopped, also at F.

Potentiometers PA, PD, PV, and PRV have their sliders on their ground terminals. The output voltages from program units NA and NR are zero.

Then, apparently, all inputs to A will receive zero currents, and the output of A is nil.

Simulation of starting the engine The pilot connects park plug PP, opens the fire-protection valve by actuating F, and starts the fuel pump through P. Relay 8 falls back as the battery voltage is cut ofi? from wire VIII.

The pilot pushes button S for engine protection and this action energizes relay 27 in the starting and ventilation program unit (PV-I-PD). Relay 27 prepares the energization circuit for relay 22. The pilot presses the button D, start of the engine, and relay 24 is activated to Work; this energizes relays 23 and 21; consequently, relays 22 and 25 come to work and motor MD begins to rotate in the normal direction developing the starting program on potentiometer PD. Relay 11 comes to work and consequently relay 4 falls back. Relays 8, 7, 5-6 at rest and relay 12 at work connect wire PD to the input of A The pilot observes the tachometrie indicator T and when the simulated speed of rotation of the engine reaches a predetermined range of values, he pushes the gas handle to slow position de-energizing relay 14. Relay 12 remains energized through the work contact of relay 18 untilshaft N1 reaches an angular position corresponding to the end of the slow period; at this instance, the battery is disconnected from I and relays 1-2, 9, 17, and 12, fall back to rest. Consequently, relay 3 is also de-energized. The input of A is then connected through c (in its left-hand position) to the output of potentiometer MG2, andthis input voltage represents a control from the power control actuated by the pilot.

When the starting program ends, cam CD de-energizes relay 21 and consequently relays '25 and 22 fall back, which reverses the supply of motor MD. Motor MD rotates backward to its initial condition. Cam CD marking the beginning of the motor run causes relay 24 to come to rest, and relay 23 is de-energized. Unit (PD-I-PV) isagain at rest.

F alS-e starts When the pilot actuates switch S during a starting period relay 27 is de-energized and relay 22 comes to rest. Motor MD is stopped and then fed for a backward rotation. In order to simulate the slow and delayed slowing of the engine, due to its high inertia thereof, a DC. current is introduced through a work contact of 23 into another winding of the motor.

The monitor may press upon button FD to simulate a false start; then relay 26 falls back and cuts oil the circuit of relay 22. The engine stops just as explained above.

The pilot may re-start the engine without waiting for the device to come to a complete standstill. In this case, he only has to operate switch S again, if necessary.

Extinction of the flame and re-ignition during flight This default may be simulated from the monitors desk during a simulated flight by action on button AR. This action controls relay 13 to its work conditionand resets to work relay 12 which is then maintained through the rest contact of 18 and the rest contact of 20 which are serially connected. Relay 3 is energized and the free rotation analog voltage NA is applied to the input of A1. V

For simulating a reignition. during flight, the pilot must bring the gas handle to its position stop? thus energizing relay 14. Relay 8 is at rest since the fire protection valve F is opened and the fuel pump is activated. Then the pilot turns switch R to reignition during flight and relays 7 and 19 are set on. If conditions-suitable to such reignition are satisfied, cams CVR and CHR will apply battery voltage to XI operating relay 38. Since these conditions imply that the speed of rotation of the turbine is lower than the speed defined above, relays 17, 9 and 12 are on.

In the program of reignition during flight, the voltage of the battery is applied, in unit (PRV), to wire XI energizing relay30. Since this battery voltage is further applied to I, relay 31 is energized and then relay 29 which is self-sustaining; consequently, relay'3t) is permitted to change over to its on-condition. Motor MR begins to rotate in the suitable direction for developing the reignition program on potentiometer PRV. The output voltage from potentiometer PRV is applied through contacts of relay 7, being in the on-condition, relay -6 being at rest and 1-2 at work, to oneinput of A wherein it is added to the free rotation voltage applied through the work contact of relay 3 to amplifier A When the pilot sees from the tachometer indicator that the speed of rotation of the engine is on the rise again, he brings the gas handle to the slow position. Relay 14 falls back, but 12 remains energized. When the angular position of N shows the speed rise beyond the maximum value of this slow condition, relays 1-2, 9 and 17 fall back to the off condition. Since relays 38 and 19 are at work, relay 20 comes to the on condition and relay 12 to the OE condition. Relay 3 is also set back to rest. The input to A then only depends 'upon the adjustment of power by the pilot. Relay 31 in (PRV) has also been de-energized but relay 29 remains activated as long as cam CR has not cut the battery voltage from the sustaining circuit of this relay. Relay 30 drops when the conditions of reignition during flight are again not met. This occurs after relay 20 has been energized. The direction of rotation of MR is then reversed and brings back potentiometer PRV to reset, and in this position, cam CR cuts the sustaining circuit of 32 which falls back to rest. Relay 23 has been de-energized by the drop of relay 30.

Ventilation When the pilot pushes button D, the process is activated and develops, as stated for the starting operation of the engine.

Stopping of the engine on the ground At the end of a simulated flight, the pilot must stop the engine and therefore, brings the power control to stop. The speed of the turbine decreases and at the required instant, the discriminator SI of direction of speed change places the armature 0 to battery. When the simulated speed has decreased to the point at which battery is applied to I, relay 9 is energized and, relay 11 being at rest and relay at work, the battery vo1tage reaches IV which actuates to work relay 4. In unit PA, relay 34 is brought on. On one hand now, the input of summing amplifier A is connected to the slider of potentiometer PA and, on the other hand, motor MA is started to rotate in the suitable direction. From the action of relay 34, relays 35 and 37 are sequentially controlled to work and the self-sustaining relay 36 is actuated. At the end of the run of MA, contact CA releases relay 34, and motor MA reverses its direction of rotation. At the return to rest of the motor shaft, contact CA opens and disables relay 36. Relays 35 and 37 have been returned to rest together with 34. During the time interval of this return to standstill program, relay 14 was on; so were 12 and 3, causing the voltage from PA to be received at A the voltage from NA then being zero. The voltage from PA simulates the inertia of the engine during its free run up to standstill.

Slowing during a flight As stated above, discriminator SI operates and potentiometers MG and MG follow the changes of position of handle MG. Circuit NR follows a law of fluctuation of voltage of predetermined rate. This voltage variation is applied to A under the control of operation of S1 This effectively simulates the. dead time interval of engine response to a control from the pilot.

Regulator default (or breakdown) 7 Such a default is simulated by the monitor actuating 10 PR on his desk, and the pilot must detect this default from the indication of the tachometer indicator T. The pilot must act to compensate this default by means of the power control.

Remark: It is noted that, during the period of simulation of a reignition during a flight, the pilot has been obliged to pass from re-ignition to normal at a speed of engine rotation of which he has been previously taught to recognize as being the speed of lesser stress on the engine. Such an action has brought relays 19 and 7 to rest, but that is without any importance since, for such a speed, the development of the reignition program was actually terminated.

Blast-pipe temperature simulator Amplifier A controls SM in accordance with the cases stated above. Servo-mechanism SM has an outputshaft controlling the computer S0 of the temperature changes of the simulated blast-pipe of the engine. An example illustrating this computer is shown in FIG. 5.

This example applies to a case where in steady operation of the engine, the temperature change is produced by the summation of a primary term, determined by the speed of the engine, and a corrective term determined in accordance with the altitude of the simulated airplane. It includes a servo-mechanism SM consisting of an amplifier/motor block or unit B a potenti ometer P for the position controlling feedback and a further potentiometer P controlled by the parameter H for the tachometric feedback. The temperature. parameter 0 is then mechanically available as the angular position of shaft N and also as an electrical signal on the potentiometer P The temperature indicator is shown at 0 and of course, placed on the pilot board.

The input of B may receive various analog voltages. Among them is a voltage of default derived from a potentiometer P0 and at the disposal of the monitor, and to which the pilot must react. There also is a reference voltage r, and two pairs of voltages, one or the ,other of which will be applied to B ,.depending upon condition of a relay 3940. This relay is controlled together with relay 12 of FIG. 3, and although itisshown separately, it may be combined with relay 12 in the form of a suitable number of armatures. Similar to relay 12, relay 3940 is provided to simulate any intempestive stopping of the engine.

Two cases will be considered:

(1) The airplane on ground and the pilot effecting a start of the engine;

'(2) The airplane in flight and the monitor having simulated an incidental extinction of the flame and the pilot acting to eifect an operation of reignition' during a flight.

and 1-8 of FIG. 3 (all these relays may be combined into relays having a sufficient" numbero'f armatures, as stated previously, for other relays of the structure).

In case 1, a start of engine operation and the changeover contact of 41- causes avoltage to be applied to 8M representing a program temperature. with respect to the development of the enginestarting operation, potentiometer PD being driven from shaft N of SM in FIG. 3. f

In case 2, the change-over of 41 applies to servomechanism 8M the analog voltage of a temperature program set for reignition of the engine during a flight, potentiometer PRV being driven from shaft N In both cases, a corrective term related to the atmosphere temperature is added to the input ofv B from a potentiometer driven by the external temperature parameter 0,. This parameter is produced by a special computer driven inrelation to H and putting to use, apart from an analog voltage depending on the function temperature/height, various auxiliary parameters which need not be specified for the purpose of the present disclosure.

Once the simulated flight is initiated, relay 3940 is at rest. The input of B receives from a potentiometer H a corrective term, related to the altitude H, and it receives a main term either from a potentiometer MG driven with MG and MG of FIG. 2 (power control of the pilot), or from a potentiometer S driven by the shaft N of SM of FIG. 3. This requires a switching operation caused by relay 42 placed under the following control. Relay 42. is energized when a changeover contact c' passes to the condition opposite to that shown in the drawing. This occurs when contact 0' being as shown, a battery voltage is applied to it through a cam C on shaft N of SM Contact c is controlled by discriminator S1 of FIG. 2. This means that contact 0' will come to the other position each time the speed of the engine will be lower than the value defined by the position of the gas handle of the pilot. Cam C is attached to shaft N in such angular position as to establish the connection to battery when the speed of rotation of the engine depending upon the position of this shaft is lower than a predetermined value but higher than the maximum slow value as defined above (the pilot has slowed down and this value is that from which there is a dead range in the response to the control of the pilot).

Force exerted by the engine and fuel consumption of such computers. It cannot be supplied from shaft N of the SM of FIG. 3 because in this unit when a deceleration occurs, thrust and consumption computers must show a sudden drop of their data whereas, as stated before, the speed of rotation of the engine must decrease at a linear law for simulating the inertia of the engine. This is the reason why, as shown in FIG. 6 (partly ShOW- ing again in FIG. 1), these latter computers are driven from a servo-mechanism SM and output shaft N separate from 5M and including certain details for the control of these computers.

In FIG. 6 an amplifier-motor unit B receives from X the output signalof A of FIG. 1 (and FIG. 2) and may receive from the monitors control an additional disadjustment voltage from a potentiometer PR In such a case, the pilot must read an abnormality on his control panel, and acts to remedy it. Unit B; is provided with a normal tachometer potentiometer P for a position.

controlling feedback circuit and, through a loop passing through a potentiometer actuated by, H; this servomechanism is further looped with respect to the speed feedback each time a relay 43 is not energized, the change overcontact of such relay being in the position shown on the drawing. When a decrease of speed is simulated, discriminator SI of FIG. 3 acts to control, from a change in position of contact 0 the supply of relay 43 and consequently, the looping of .servomechanis-m 5M in a mere position feedback. The result is a sudden decrease in the speed of rotation of shaft N and a subsequent decrease or drop of the output voltages simulating at SP and SC the thrust and fuel consumption in these computers.

I claim:

1. In a system for simulating the operation of a turbojet engine in which fuel and gas temperature are regulated automatically at optimum admissible values for any control conditions selected by the operator, a summing amplifier, a servo-mechanism controlled by the output of said summing amplifier, and means for indicating the engine speed including at least one shaft driven by said servo-mechanism in linear relation with said speed, pilot controlled means and monitor controlled means, means under the control of said pilot controlled means and said monitor controlled means for producing a corresponding number of analog voltages representative respectively of definite speed functions corresponding to distinct conditions of control of said turbo-jet engine, said pilot controlled means including means for applying voltages representing respectively simulation of power controlling gas admission, slow and free engine rotations, an automatic starting program, a ventilation program, a stopping program, and a reignition program; the stopping program being also operable by means included in said monitor controlled means and further including means for applying a stopping program during flight; means under the control of said flight stopping program to control the application of free engine rotation voltages, and means for initiating said reignition program, including computing means for deriving flight speed and height simulations and means under the control of said computing means for operating said reignition program so that, at decreasing servo-speed, upon said speed decreasing below a value determined ,by said flight simulations, reignition voltage is added to said free rotation voltage until a simulated speed of rotation is reached corresponding to the operativeness of said slow rotation program and means under the control of said controlled means and said servo-mechanism for selectively routing said analog voltages to inputs of said summing amplifier so as to indicate engine speed as the result of the various voltage conditions imposed by said controlled means and the engine speed itself.

2. System according to claim 1 comprising a tachometer controlled by said shaft of said servo-mechanism, and monitor controlled and means for applying an additional input to said amplifier simulating a default of operation of said speed regulator causing a change of tachometer indications.

3. System according to claim 1 wherein said re-ignition program means include two voltage sources representing re-ignition on ground and during flight, respectively, and two position switching means under control of said pilot controlled means to selectively connect one of said sources to said routing means.

4. System according to claim 1 comprising switching means in said pilot controlled means for selectively applying ventilation program and starting voltage programs to the input of said routing means, a common clock mechanism controlling both said voltage programs; said ventilating and starting voltage programs being substantially identical with the exception at least of means simulating fuel supply being included in said starting voltage program only.

5. System according to claim 1 comprising means for computing speed and altitude simulations for the plane, said re-ignition program is operative under the control 7 of said computing means after compliance with speed and altitude of the plane and speed of the engine, there being provided means in said monitor controlled means under the control of said computing means for displaying simulations of speed and altitude of the plane as well as engine speed.

6. System according to claim 1 comprising first means for computing speed and altitude simulations for the plane and further computing means under the control of said first computing means. for producing voltages simulating blast pipe temperature under the control of said shaft of said servo-mechanism.

7. System according to claim 1 comprising a second servo-mechanism under the control of said amplifier output, thrust computing means and fuel consumption com- 13 puting means both under the control of a shaft of said second servo-mechanism.

8. System according to claim 1 comprising means for computing speed and altitude simulations for the plane, both said simulations of slow engine rotation and of free engine rotation being under the control of said computing means, means for comparing the gas admission voltage with said slow-engine voltage, t'wo position switching means under the control of said comparing means for passing in one position, at minimum slow-speed, voltage from said slow-speed program means to said routing means and, in another position, at maximum slow-speed, voltage from said gas admission voltage means to said routing means.

9. System according to claim 1 wherein said starting voltage program means also include means simulating gas admission; said power control means being adjustable in positions having a stop position simulating cutoff of fuel supply and a slow-speed position simulating restriction of fuel supply; the speed of rotation of the engine being determined by the position of said power control means only once it has passed said slow-speed position.

10. System according to claiml comprising means for computing reference speed voltages depending at least on altitude simulation and means providing a dead span behind said slow-speed position including voltage sources varying under the control of saidpower control means, means for comparing reference and source voltages and means under the control of said comparing means for switching from reference to source voltages; said dead 14 span dependent upon simulation of altitude representation.

11. In a system for simulating the operation of an automatically regulated jet engine, a summing amplifier, a servo-mechanism controlled by said summing amplifier, a tachometer driven by said servo-mechanism, pilot controlled means and monitor controlled means, said pilot controlled means including means for applying to said summing amplifier analog voltages representing, respectively, simulation of power control, slow and free engine rotations, a stopping program and a reignition program; the stopping program being also operable by means included in said monitor controlled means and further including means for applying a stopping program during flight; means under the control of said flight stopping program to control the application of free rotation voltages, and means for initiating operation of said reignition program flight speed and height simulations including means for computing, and means under the control of said computing means for operating said reignition program so that, at decreasing servo-speed, upon said speed decreasing below a value determined by said flight simulations, reignition voltage is added to said free rotation voltage until a simulated speed of rotation is reached corresponding to the start of said slow rotation program.

Stern-et al July 9, 1957 Dawson Apr; 21, 1959 

